Traumas as well as congenital disorders cause bone and soft tissue defects in oral and maxillofacial region. Periodontal disease results in destruction of alveolar bone and tooth loss. The ultimate therapeutic goal for these diseases is tissue regeneration, which requires (1) differentiation of reparative cells and (2) production of extracellular matrix components. Our long-range goal is to expand current understanding of the cellular and molecular mechanisms involved in formation and regeneration of periodontal tissues and to provide further insight into the development of products for skeletal regeneration and tissue engineering. The objective of this application is to determine differentiation potential of cells involved in the processes of tissue repair and regeneration. The central hypothesis to be tested is that, in periodontal regeneration, the transcription factor Cbfa1 selectively induces osteogenic and cementogenic differentiation and the subsequent expression of BSP which enhances tissue formation and mineralization. The rationale is based on evidence that the conversion of non-differentiated mesenchymal cells and pre-osteoblastic cells into mature and functional osteoblasts is a crucial step in bone formation, as well as in bone regeneration. Aim 1. To determine in vivo the regulating and promoting effects of Cbfa1 in cell differentiation occurring during periodontal regeneration. Using a gene-therapy approach, for the first time, the "master gene" Cbfa1, will be introduced into an artificially created periodontal defect and its inductive and modulating effects documented. Aim 2. To determine the role of BSP expressed by differentiated cells in enhancing mineralization in the process of bone tissue formation and regeneration in rive. Using a cell-based method, BSP overexpressing cells will be transplanted into periodontal defects and for the first time the effect of BSP in enhancing biomineralization and bone maturation in vivo determined. Results derived from these in rive studies should provide novel and important insights into osteogenic gene therapy and molecular control of differentiation of cells, the most important component and the most powerful engine in tissue formation and periodontal regeneration.